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To keep his heart healthy, cardiologist Brent Muhlestein takes 5,000 units of vitamin D a day — a habit he will continue despite a new report claiming there is no evidence that the vitamin provides much benefit beyond strengthening bones.
Calling the Institutes of Medicine report released Tuesday "overly conservative," Muhlestein points to his own studies at Intermountain Healthcare that suggest higher levels of vitamin D translate to better heart health.
"I tend to trust my own studies," said the director of cardiovascular research at the Heart Institute at Intermountain Medical Center. "Our observational studies still demonstrate a significant association between cardiovascular risk and vitamin D insufficiency."
With media reports touting the vitamin for reducing the risks of diseases including autoimmune diseases, cancer and diabetes, an Institutes of Medicine committee assessed 1,000 studies and reports to clarify the benefits and offer advice on how much to take.
"This thorough review found that information about the health benefits beyond bone health — benefits often reported in the media — were from studies that provided often mixed and inconclusive results and could not be considered reliable," says the report.
It also found that most Americans receive adequate amounts.
Muhlestein disagrees. Tapping medical records for more than 41,000 Intermountain patients, he found only one-third had sufficient levels in their blood. Found in few foods, the vitamin mainly comes from sun exposure. But sunscreen blocks absorption, and Utah's latitude reduces the UV radiation exposure needed for vitamin D synthesis.
And while the IOM recommends adults get 600 international units a day, Muhlestein says a blanket recommendation doesn't make sense. Instead, patients' vitamin blood levels should be tested first, he said.
That's how he came up with his own "prescription" of 5,000 units a day: Less didn't boost his levels enough, even though the IOM report says 4,000 units should be the upper limit for adults.
An Intermountain study recently published in the American Journal of Cardiology found that patients who were vitamin D deficient but had no other cardiovascular risk factors were at an increased likelihood of developing diabetes, hypertension and high cholesterol.
Other Intermountain studies have linked deficiency to heart failure, stroke, coronary artery disease and death.
"My guess is there is a cause and effect relationship," Muhlestein said, while acknowledging the need for a trial that would randomize deficient patients to taking the vitamin or a placebo. His studies have been observational.
One Intermountain study that hasn't been published showed that deficient patients who boosted their vitamin D levels were less likely than others to have cardiovascular problems, he said.
"It appears that if you do something about your vitamin D level, it will reduce your risk," he said.
Reporting on vitamin D
A new Institutes of Medicine report found:
Research so far cannot confirm that vitamin D protects against cancer, heart disease, autoimmune diseases or diabetes.
Most Americans and Canadians up to age 70 need no more than 600 international units (IUs) of vitamin D per day.
Those age 71 and older may need as much as 800 IUs.